1. Field of the Invention
This invention relates to a novel active material-protecting structural compositions which protect an active material core with a sheath and more particularly to such compositions where said active material is either catalysts or adsorbent.
2. Description of the Prior Art
Heretofore, an active material e.g. catalyst, adsorbing agent etc. to be used in vapor phase or liquid phase reactions has been used in a form of powder, or granules prepared of the material itself or admixed of a binder, or adsorbed on a supporting carrier. However, when the active material is used in power form, especially in vapor phase reactions, it requires special design to maintain the powder in a fluid condition. Considerable loss is caused by crushing the powder in fine particles. When the active material is used in liquid phase reactions, separation of the powder from the liquid, is troublesome and continuous operation is difficult. When the active material e.g. catalyst, or adsorbing material is used in the form of granules, some of the disadvantages are eliminated. However, when the active material is granulated, there are certain other drawbacks including a decrease of activity of the material, catalytic or adsorbing activity or low crush strength, impact strength or abrasion strength of the granules. Even though the granules have enough strength at the beginning of their use, the strength gradually or rapidly decreases. during use and continued operations become difficult because of powdering or other forms of decrepitation.
Moreover, when a carrier is used, the active material is often removed from the carrier, and the resultant decreased activity is difficult to overcome.
It is also difficult to increase the ratio of the active ingredient to support while maintaining the proper activity.
It is quite important, in industrial and practical cases using the active material, to overcome the disadvantages caused by powdering of the granules of active materials.